When first completed, many gas wells have sufficient reservoir pressure to flow formation fluids to the surface along with the produced gas. As gas production continues, the reservoir pressure declines, and as pressure declines, the velocity of the fluid in the well tubing decreases. Eventually, the gas velocity up the production tubing is no longer sufficient to lift liquid droplets to the surface. Liquids may then accumulate in the tubing, creating additional pressure drop, slowing gas velocity, and raising pressure in the reservoir surrounding the well perforations and inside the casing. As the bottom well pressure approaches reservoir shut-in pressure, gas flow may stop and liquids can accumulate at the bottom of the tubing.
At different stages in the life of a gas well, various means can be employed to move accumulated liquids to the surface. These may include foaming agents or surfactants, velocity tubing, plunger lift, and downhole pumps. The proper application of pumps can lower the abandonment pressure of wells, increasing reserves captured per well, and reduce the number of wells required to economically deplete an asset.
Micro positive displacement and solid state pumps are currently being developed for installation in field applications. Given the nature of these pumps and their valving, filtering of the intake fluid may be required. As such, the potential for plugging screens and/or filters can be a concern. In some configurations, screen and filter cleaning or replacement may be costly, since the complete removal of the deployment cable and pump may be required.
Therefore, what are needed are improved systems and methods for maintaining downhole pumps and cleaning the upstream filters and screens of downhole pump-based systems.